Update vendored procfs for buddyinfo, mountstats, and XFS changes

vendor/github.com/prometheus/procfs/fs.go

@@ -4,6 +4,8 @@ import (
 	"fmt"
 	"os"
 	"path"
+
+	"github.com/prometheus/procfs/xfs"
 )
 
 // FS represents the pseudo-filesystem proc, which provides an interface to
@@ -31,3 +33,14 @@ func NewFS(mountPoint string) (FS, error) {
 func (fs FS) Path(p ...string) string {
 	return path.Join(append([]string{string(fs)}, p...)...)
 }
+
+// XFSStats retrieves XFS filesystem runtime statistics.
+func (fs FS) XFSStats() (*xfs.Stats, error) {
+	f, err := os.Open(fs.Path("fs/xfs/stat"))
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	return xfs.ParseStats(f)
+}